If you convert the audio file to a Quicktime audio movie, the player actor allows you to set the number of eq channels that it can output for you.
So.
If your file is a .wav or similar you can open if you favorite audio software and save as quicktime (or mp3 is read the same way).
Import it to Isadora and use the 'Sound Movie Player' actor for playback. Adjust the 'freq bands' input to set the number of output channels... and you should be set.

In 2.0 the Ayer has an eye icon that hide/reveals additional features. Just double click the icon and active the features you want. If it's a live source you need to set it up as a live capture input and use the frequency watcher. You need one actor setup for each frequency.